Coupling device and improved method of assembly thereof

ABSTRACT

A coupling device ( 11 ) and method of assembly, the device being of the type including a plenum member ( 17 ) disposed at one axial end of the coupling housing ( 13,15 ), the method comprising configuring the plenum member ( 17 ) such that each of the required features ( 55,57,61,66 ) is disposed circumferentially between an adjacent pair of fastener holes ( 18 H). Next, the input ring gear (R) is installed about the housing ( 13,15 ) of the coupling device ( 11 ), from an axial end opposite said plenum member ( 17 ), into assembly position adjacent said flange portion ( 18 ). Each of a plurality (N) of fasteners ( 89 ) is inserted through one of the fastener holes ( 18 H) and into initial threaded engagement with the input ring gear (R). Finally, by means of a fastener driver, all of the plurality (N) of fasteners ( 89 ) are driven into full threaded engagement, substantially simultaneously, with the input ring gear (R).

BACKGROUND OF THE DISCLOSURE

The present invention relates to coupling devices of the type used totransmit torque, for example, in a vehicle drive line, and moreparticularly, to a coupling device of the type having a bevel gear ringgear associated therewith as the input to the coupling device. Thepresent invention also relates even more particularly to an improvedmethod of assembly of such a coupling device.

As used herein, the term “coupling device” will be understood to meanand include a device which is able to transmit torque from an input toone or more outputs, and in which there is a clutch assembly disposedbetween the input and the output, such that the torque transmission ofthe coupling device is in some way related to the extent of engagementof the clutch assembly. Within the scope of the present invention, theterm “coupling device” means and includes both gear-type devices (suchas bevel gear differentials), as well as gearless-type (clutch only)coupling devices.

Although the improved method of assembly of a coupling device may beutilized with many different types and configurations of couplingdevices, such as coupling devices made in accordance with the teachingsof U.S. Pat. No. 5,964,126, assigned to the assignee of the presentinvention and incorporated herein by reference, it is also quiteadvantageous when utilized in conjunction with vehicle differentials ofthe type illustrated and described in U.S. Pat. No. 5,310,388, alsoassigned to the assignee of the present invention and incorporatedherein by reference. It is believed that those skilled in the art ofdifferential and coupling devices will have a much better understandingof the potential scope of the present invention from a reading andunderstanding of the remainder of the specification.

A common factor in most differentials and coupling devices, of the typeto which the present invention relates, is the presence of some sort ofannular input ring gear (typically, of a “bevel” gear configuration)which serves as the “input” to the coupling device, in terms of thetorque flow path. Typically, input drive is transmitted from the vehicledriveline by means of an input pinion gear to the ring gear, in a mannerwell know in the driveline art. Also typically, the housing of thecoupling device defines a radially extending flange portion, and theannular ring gear is disposed about the housing of the coupling deviceand is fastened to the flange portion, typically by means of a pluralityof bolts. The coupling device is normally manufactured by someone suchas the assignee of the present invention, and is then shipped to theaxle or vehicle assembly plant where the coupling device and the ringgear are fastened together, and then the entire coupling device-ringgear subassembly is installed within an outer differential housing. Asis well known to those skilled in the art, it is typically the outerdifferential housing which serves as a fluid reservoir (low pressuresource) for the lubrication fluid required for use in the couplingdevice. In the coupling devices of the cited patents, there is includeda clutch pack operable to transmit torque between the input (thecombination of the ring gear and the coupling housing) and the output(one of the axle shafts). The degree of engagement of the clutch pack isdetermined by fluid pressure in a piston chamber in which the fluidpressure biases a clutch piston against the clutch pack. Thedifferential coupling devices of the cited patents include a gerotorpump, integral with the coupling device, the gerotor pump having onerotor fixed to rotate with the input and the other rotor fixed to rotatewith the output. As used herein, the term “clutch pack” will beunderstood to mean and include not only a multiple friction disk-typeclutch pack, but also, any of the other well known types of clutchassemblies, such as cone clutches, etc. in which the degree ofengagement is generally proportional to the fluid pressure acting on theclutch piston, or on an equivalent clutch-engagement structure.

It should be understood that the present invention is not limited to acoupling device of the type that includes a gerotor pump, nor to acoupling device having any particular type of clutch and clutch pistonarrangement, except to the extent specifically noted hereinafter in theappended claims. However, as will be understood by those skilled in theart from a reading and understanding of the subsequent specification,the assembly method of the present invention is more likely to be ofbenefit, and be needed, in conjunction with a coupling device havingsome sort of “on-board” source of fluid pressure (such as a gerotorpump) which serves as the source for pressurized fluid in the clutchpiston chamber. Furthermore, the assembly method of the presentinvention is especially advantageous if the coupling device includessome sort of pressure control valve assembly for controlling theinstantaneous fluid pressure in the piston chamber, in response to theneed for torque transmission through the coupling.

In the differential coupling device of the present invention there isdisposed about one end of the coupling housing a plenum member whichserves, in part, to define a substantial portion of the hydrauliccircuit which controls the piston apply pressure in the piston chamber.In the subject embodiment of the invention, this plenum member defines anumber of required “features” as that term will be amplified anddescribed in greater detail subsequently, one example of such a“feature” being a portion which extends radially downward into the lowpressure reservoir, or sump, defined within the outer differentialhousing and which therefore serves as the “inlet” to the hydrauliccircuit. Another example of such a “feature” is a portion which extendsradially outward from the plenum member, and on which the pressurecontrol valve assembly is mounted.

In developing a commercial embodiment of the present invention, it wasdetermined that, partially because of such required “features” on theplenum member, the assembly process was greatly complicated and, as aresult, made unacceptably expensive. It is well known to those skilledin the art of assembling such differential coupling devices, that thepreferred method of assembling the coupling device and the ring gear inthe axle or vehicle assembly plant is to manually insert each of thefasteners through the flange portion of the housing and partially threadthe fasteners into the ring gear. Subsequently, the assembly operatorwould use a bolt driver, having a separate driver for each of thefasteners, such that all of the fasteners are fully threaded into thering gear simultaneously. However, on the coupling device of the presentinvention, the ring gear is installed from one end of the couplinghousing, until it is seated in a face-to-face relationship with theflange portion. The plenum member is disposed at the opposite axial endof the coupling housing, and therefore, the fasteners must be insertedthrough the flange portion and into the ring gear from the end of thecoupling housing where the plenum member is disposed, and in addition,the bolt driver must be able to engage each of the bolts from the endwhere the plenum member is disposed.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide animproved coupling device, and an improved method of assembly thereof, inwhich the plenum member has all of its required structural features, butin which it is still possible to drive all of the fastener membersthrough the differential coupling device flange portion into the ringgear, simultaneously.

It is another object of the present invention to provide such animproved coupling device and method of assembly thereof which makes itpossible for the relatively more critical steps of the assembly processto be performed in connection with the manufacture of the couplingdevice, while primarily the relatively less critical steps of theassembly process (except for the critical step of tightening the ringgear fasteners) are left to be done in the vehicle (or axle) assemblyplant.

The above and other objects of the invention are accomplished by theprovision of an improved method of assembly of a coupling device to aninput ring gear, for eventual installation within an axle housing, thecoupling device including a housing defining a clutch cavity, a clutchassembly disposed in the clutch cavity, a clutch apply member disposedin a pressure chamber and operable to bias the clutch assembly intotorque transmitting relationship in response to the presence ofpressurized fluid in the pressure chamber. The coupling device includesa plenum member operably associated with the housing to define a fluidflow path providing fluid communication between a reservoir disposedwithin the axle housing and the pressure chamber, the fluid flow pathbeing in fluid communication with a source of pressurized fluid. Thehousing includes a flange portion defining a plurality of fastener holesand being adapted to have the input ring gear attached thereto by meansof a plurality of fasteners. The plenum member comprises a generallyannular plenum portion, and a plurality of required features extendingradially from the plenum portion.

The improved method of assembly comprises the steps of:

-   -   (a) configuring the plenum member such that each of the required        features is disposed circumferentially between an adjacent pair        of said fastener holes;    -   (b) installing the ring gear about the housing of the coupling        device, from an axial end opposite the plenum member, into        assembly position adjacent the flange portion;    -   (c) inserting each of the plurality of fasteners through one of        the fastener holes and into initial threaded engagement with the        input ring gear; and    -   (d) driving, by means of a fastener driver, all of the plurality        of fasteners into full threaded engagement, substantially        simultaneously, with the input ring gear.

In accordance with a more limited aspect of the invention, one of therequired features defined by the plenum member comprises a fluid inletportion extending radially toward the reservoir, and another of therequired features comprises a valve mounting portion, the couplingdevice including an electromagnetic valve member, operable to controlfluid pressure in the fluid path, the method of assembly comprising thefurther step, subsequent to the step (d), of operably attaching thevalve member to the valve mounting portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross-section of a vehicle differential coupling ofthe type with which the present invention may be utilized.

FIG. 2 is a perspective view of the differential coupling device afterassembly thereto of the input ring gear.

FIG. 3 is a plan view of the coupling device and ring gear assembly,viewed from the left end in FIG. 1, illustrating certain key aspects ofthe present invention.

FIG. 4 is a fragmentary plan view of the outer differential housingafter the coupling device has been installed therein, but with the ringgear omitted from the view for ease of illustration.

FIG. 5 is an enlarged perspective view of the pressure control valveassembly, as it is prior to assembly into the coupling device.

FIG. 6 is a fragmentary, partly broken away view the plenum member, withthe pressure control valve assembled thereto, in accordance with oneaspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, which are not intended to limit theinvention, FIG. 1 illustrates a differential coupling device, generallydesignated 11, for use in a vehicle drive line, and which is of thegeneral type illustrated and described in the above-incorporatedpatents, and which is especially well-suited for use in connection withthe assembly method of the present invention. The differential couplingdevice 11 comprises a housing, including a gear housing 13, a clutchhousing 15, and a valve housing 17, held together by any suitable means,well known in the art. In a manner well known to those skilled in thedifferential art, the gear housing 13 and the clutch housing 15cooperate to define a radially extending flange portion 18 (shown onlyin the bottom half in FIG. 1), and disposed adjacent to the flangeportion 18 is an annular ring gear R, shown somewhat pictorially in FIG.2 with the teeth not being visible. The flange portion 18 defines aplurality of fastener holes 18H, to be used to fasten the ring gear R tothe flange portion 18, as will be described in greater detailsubsequently.

Referring still to FIG. 1, the gear housing 13 defines a gear chamber19, and disposed therein, but by way of example only, there may beprovided a typical differential gear set. In the subject embodiment,there is included a pair of input pinion gears 21, rotatably mountedrelative to a pinion shaft 23, the pinion gears 21 being in toothedengagement with a pair of side gears 25 and 27. In the subjectembodiment, and again by way of example only, the input pinion gears 21(along with the ring gear R and the housings 13 and 15) may beconsidered the “input” to the coupling device 11, while the side gears25 and 27 (and the axle shafts which would be splined thereto) comprisethe “outputs” of the coupling device 11. More specifically, for purposesof most of the subsequent description, the side gear 27 will beconsidered to comprise the “output” of the coupling 11.

The side gears 25 and 27 define sets of straight, internal splines 25Sand 27S, respectively, which are adapted to receive right and left axleshafts (not shown herein), whereby the coupling device 11 transmitstorque by means of the axle shafts to associated vehicle drive wheels(also not shown). It should be clearly understood, however, that thestructure described hereinabove is by way of example only, and themethod of assembly of the present invention may also be used withvarious other types of structures.

Referring still primarily to FIG. 1, there is disposed within the clutchhousing 15 a clutch pack, generally designated 29, which, as is wellknown to those skilled in the art, typically comprises a plurality ofouter disks (no reference numeral herein) which are in splinedengagement with a set of internal splines defined by the clutch housing15. In addition, the clutch pack 29 would typically include a pluralityof inner disks (no reference numeral herein), which are interleaved withthe outer disks in a well known manner, the inner disks being in splinedengagement with a coupling member 35. The coupling member 35 defines aset of internal splines 35S which are also in splined engagement withthe left axle shaft, such that the coupling member 35 is fixed, in thesubject embodiment, to rotate with the side gear 27.

Also disposed within the clutch housing 15 is an annular housing insert37 which cooperates with the adjacent coupling member 35, and with theclutch pack 29, to define a clutch cavity or clutch piston chamber.Disposed within the clutch piston chamber, and moveable axially therein,is a clutch piston 41 which cooperates with the housing insert 37 todefine a piston pressure chamber 43. As is well known to those skilledin the art of such devices, variations in the fluid pressure in thepiston pressure chamber 43 will result in variations in the axial forceapplied by the clutch piston 41 to the clutch pack 29 and therefore,will result in variations in the “bias torque”, i.e., the torquetransmitted through the clutch pack from the input of the coupling 11 tothe output.

Referring still primarily to FIG. 1, also disposed within the clutchhousing 15, and immediately to the left of the housing insert 37, is agerotor pump, generally designated 45, which is well known from theabove-incorporated patents, and will not be described in detail herein.As is now well known to those skilled in the art, the gerotor pump 45would include an inner rotor 47 defining a set of straight, internalsplines 47S which are also in engagement with the left axle shaft, asdescribed previously, such that the inner rotor 47 is fixed to rotatewith the coupling member 35 and the side gear 27. During normal,straight-ahead operation, the entire differential coupling 11 rotates asa unit, i.e., the ring gear R, the housings 13 and 15, and the sidegears 25 and 27 (as well as the axle shafts splined thereto) all rotateat the same rotational speed. In that condition, there is no relativerotation between the rotors of the gerotor pump 45, and therefore, thereis no pumping of pressurized fluid from the volume chambers (formedbetween the teeth of the rotors when they are relatively rotating).

As is also well known to those skilled in the coupling device art, basedin part upon the teachings of the above-incorporated patents, when thereis differentiation, i.e., when there is a difference in the speed ofrotation between the left and right axle shafts, there will also, ofnecessity, be a speed difference between the coupling input and theoutput (the left axle shaft). That speed difference between the inputand output will result in the rotation of the left axle shaft drivingthe inner rotor 47 of the gerotor pump 45, thus pumping pressurizedfluid, such that the fluid will eventually be communicated throughappropriate chambers and ports in the housing insert 37, and thepressurized fluid is eventually communicated into the piston pressurechamber 43. The entire fluid circuit, for controlling the pressure inthe piston pressure chamber 43, as well as a preferred method forcontrolling the circuit, is illustrated and described in greater detailin co-pending application U.S. Ser. No. 10/795,651, filed Mar. 8, 2004in the name of Christopher J. Babin for a “Coupling Device And ImprovedMethod Of Controlling Torque Transmission”, assigned to the assignee ofthe present invention and incorporated herein by reference.

Referring still to FIG. 1, it may be seen that the valve housing 17(also referred to hereinafter as the “plenum member”), which isstationary within, and relative to the outer differential housing H(which is shown only in FIG. 4), receives on its inner periphery, a pairof seal members 49 which are disposed on axially opposite sides of aradial passage 51. Thus, references hereinafter, and in the appendedclaims, to the “fluid flow path” will bear the reference numeral “51”,because the radial passage 51 comprises a part of the fluid flow path,and the other portions thereof either are not visible or do not bearreference numerals in FIG. 1. The seal members 49 are in sealingengagement against the adjacent, outer cylindrical surface of a hubportion 53 formed integrally with the clutch housing 15. As may best beseen in FIGS. 2, 3 and 6, the plenum member 17 includes an inlet portion55 which, preferably, extends down into a “source” of low pressurefluid, which would typically comprise a reservoir or sump containingfluid, and being disposed within the outer differential housing H, as iswell known. The plenum member 17 also includes a port portion 57 whichdefines one or more fluid passages in communication with the radialpassage 51. As will be described in greater detail subsequently, theport portion 57 has mounted therein a pressure control valve assembly,generally designated 59, shown as a separate sub-assembly in FIG. 5, andshown installed into the plenum member 17 in FIG. 6, as will bedescribed in greater detail subsequently.

In accordance with an important aspect of the present invention, theinlet portion 55 and the port portion 57 both comprise what arehereinafter referred to as “required features” of the plenum member 17,i.e., both the inlet portion 55 and the port portion 57 are requiredparts of the plenum member 17, in order for the plenum member 17 toperform its function, which includes providing fluid to the fluid flowpath (radial passage 51) and controlling the pressure in the pistonpressure chamber 43. Certain other types of “required features” of theplenum member 17 will be discussed subsequently.

Referring now primarily to FIGS. 2 and 3, it may be seen that the plenummember, in the subject embodiment and by way of example only, includesthree additional “required features”, which include a pair ofanti-rotation tabs 61, the function of which will be described ingreater detail subsequently. The anti-rotation tabs 61 are approximatelydiametrically opposite each other, and as may best be seen in FIG. 2,extend axially from an end surface 63 of the plenum member 17, such thatthe tabs 61 would extend to the left from the end surface 63 in FIG. 1,if the view of FIG. 1 were on a plane which included the tabs 61. Theplenum member 17 also includes a plurality of spacer tabs 64, alsoextending to the left in FIGS. 1 and 2 from the end surface 63, thefunction of the spacer tabs 64 to be described subsequently. Finally,the plenum member 17 includes a wiring retention tab 66, the function ofwhich will also be described subsequently.

Referring now primarily to FIGS. 1 and 2, it may be seen that the gearhousing 13 includes a hub portion 65, which may be substantiallyidentical to the hub portion 53 of the clutch housing 15. By way ofexample only, at the end of the process of assembling the couplingdevice 11, a pair of tapered roller bearing sets 67 are pressed onto thehub portions 53 and 65, typically, both bearing sets 67 being pressed onat the same time, on an appropriately configured press station, as iswell known in the art, the details of which form no part of the presentinvention. As may be seen in FIGS. 1 and 2, the references herein to the“bearing sets” mean and include only the inner race and the rollersthemselves, but not the outer race, for reasons which will be explainedsubsequently. Once the bearing sets 67 are pressed onto the hub portions53 and 65, the juxtaposition of the left hand bearing set (i.e., theouter race of the bearing set 67, after it is subsequently added) andthe spacer tabs 64 insures that the plenum member 17 will not moveleftward in FIG. 1, away from its desired, assembled position, as shownin FIG. 1.

Although, for purposes of illustration and explanation, FIGS. 1 and 2include the ring gear R, it should be understood that typically, afterthe completion of the assembly of the coupling device 11 (including thepressing on of the bearing sets 67 as just described), the couplingdevice 11 would be shipped to the axle assembly plant, for assembly ofthe coupling device 11 into the overall axle assembly. Typically, itwould be at the axle assembly plant that the ring gear R would, for thefirst time, be assembled to the coupling device 11. As will beunderstood by those skilled in the art, in some commercial situations,the “axle assembly plant” is in reality the assembly plant at which thefinal assembly of the entire vehicle takes place. However, for purposesof the present specification, references to the “assembly plant” will beunderstood to mean and include the place of assembly of the couplingdevice 11 into the overall axle housing and assembly, whether or notthat is part of the final vehicle assembly. Furthermore, “axle assemblyplant” could even include the plant at which the coupling device 11 isassembled, if the ring gear R is also assembled there.

Referring again primarily to FIGS. 2 and 3, one additional feature ofthe coupling device 11, as it is shipped to the assembly plant, will bedescribed. In connection with the development of a commercial embodimentof the coupling device 11, it has been determined that it is desirableto have the entire fluid path 51 (hydraulic circuit) within the couplingdevice 11 filled with fluid prior to shipment, rather than having tofill the coupling device with fluid as a separate step during the axleassembly process. Filling with oil before shipment of the couplingdevice 11 is done in order to test for leaks and missing seals, andafter such testing is complete, it would be difficult and time-consumingto drain the fluid out of the coupling device prior to shipment.Finally, filling the coupling device with fluid saves the customer (axleor vehicle assembler) time, not having to “prime” the coupling device(i.e., fill it with oil) at axle assembly plant. Therefore, the inletportion 55 has a suitable oil plug 71 inserted within the opening (notshown) of the inlet portion 55. Those skilled in the art will understandthat there is also a need for a coarse filter screen 72 (shown only inFIG. 6) within the inlet portion 55 to keep out debris, metal chips, andlint. The oil plug 71 would typically comprise a molded plastic member,including a tab portion 73 formed integrally therewith. Similarly, theport portion 57 has, inserted therein, an oil plug, disposed within theport portion 57 and not visible in FIGS. 2 and 3, but which would alsocomprise a molded plastic member, including a tab portion 75, which isvisible in both FIGS. 2 and 3. In the subject embodiment, and by way ofexample only, the tab portion 75 comprises a circular loop, with the tabportion 73 of oil plug 71 passing therethrough, for reasons to beexplained subsequently, in connection with the assembly process.

Referring now primarily to FIGS. 5 and 6, the pressure control valveassembly 59 is preferably shipped to the axle assembly plant as anindividual part, separate from the coupling device 11. In accordancewith another important aspect of the invention, and as will be describedin greater detail subsequently, the pressure control valve assembly 59is of the “quick connect” type, as that term is generally well known tothose skilled in the art. By way of example only, and as may best beseen in FIG. 6, the pressure control valve assembly 59 includes a lower,inlet portion 77, adapted to be disposed within the port portion 57 andretained therein, after the assembly process of the present invention,by means of an expanding clip 79, shown best in FIG. 6. The expandingclip 79 includes a pair of radially-extending tabs 81 which, afterassembly, are in the expanded (spread apart) position shown in FIG. 6,in which the annular portion of the expanding clip 79 is in engagementwith an annular groove formed within the port portion 57, thus retainingthe valve assembly 59 therein. Those skilled in the art will understandthat various other quick-connect arrangements could be used, within thescope of the invention, to retain the pressure control valve 59 withinthe port portion 57.

Referring now primarily to FIG. 5, it may be seen that when the pressurecontrol valve assembly 59 is being shipped, the expanding clip 79 ismaintained in a “pre-assembly” position by means of a plastic retainer83, including a retainer portion 85, which surrounds theradially-extending tabs 81 of the expanding clip 79, and holds the tabs81 in a position in which they are immediately adjacent each other,i.e., the “pre-assembled” position. Formed integrally with the retainerportion 85 is an upstanding portion including a pair of tabs 86 (onlyone of which is shown in FIG. 5), which extend radially on either sideof an anti-rotation tab 59T, which is fixed relative to the housing ofthe pressure control valve assembly 59. As may also be seen in FIG. 5,the pressure control valve assembly 59 includes a portion, designated87, which comprises an electrical connector, by means of which a wiringharness may be connected to the valve assembly 59, to provideappropriate electrical input signals thereto, in a manner well known tothose skilled in the art.

As will be appreciated by those skilled in the vehicle assembly art, theeventual presence (as part of the coupling device 11) of the pressurecontrol valve assembly 59, adds substantial difficulty and potentialcomplication to the method of assembly of the coupling device 11 withinthe overall axle housing. For example, those skilled in the art willrecognize that there would not be sufficient room within the axlehousing for the valve assembly 59 to be oriented radially, relative tothe axis (i.e., the axis of rotation of the axle shafts) of the couplingdevice 11. Thus, the valve assembly 59 is located as shown in FIG. 5.However, as may best be seen in FIG. 3 (from which the valve assembly 59is omitted) it is not possible to install the valve assembly 59 prior tofastening the ring gear R to the flange portion 18. If the valveassembly 59 were already present, access to the fastener at the threeo'clock position would be blocked.

Referring now again primarily to FIGS. 2 and 3, when the coupling device11 is received at the axle (or vehicle) assembly plant, as that term waspreviously defined, it is in the condition shown in FIG. 2, except thatthe ring gear R and its fasteners are not yet part of the subassembly.The first step therefore in the actual assembly process (i.e., theassembly of the coupling device 11 within the axle housing H) is toslide the ring gear R over the gear housing 13 until it is in place,adjacent the flange portion 18, i.e., in the position shown in FIGS. 1and 2. The next step is to insert in each of the holes 18H within theflange portion 18 a suitable fastener, which, in the subject embodiment,comprises a socket head cap screw 89. In the subject embodiment, and byway of example only, there are ten of the cap screws 89, and althoughwithin the scope of the present invention, various other types offastener could be utilized, it may be seen, especially from FIG. 3, thatthe space surrounding each of the cap screws 89 is very limited, andaccess to another type of fastener, such as a hex head bolt, could bequite difficult.

In accordance with an important aspect of the invention, it may be seenin FIG. 3 that each of the “required features” defined by the plenummember 17 (i.e., the inlet portion 55; the port portion 57; and the tabs61 and 66) are all located, circumferentially, such that none of therequired features blocks access to the cap screws 89. After the ringgear R is in place, adjacent the flange portion 18, each of the capscrews 89 is disposed in threaded engagement with the ring gear R.Typically, this initial threaded engagement of each of the cap screws 89into the ring gear R is accomplished by hand by the assembly operator.Once each of the cap screws 89 is in initial threaded engagement withthe ring gear R, as shown in FIG. 3, the next step in the assemblyprocess is to utilize a specially-equipped, multi-head driver (wellknown in the art and not shown herein) which is moved into place, to bein driving engagement with all ten of the cap screws 89 simultaneously.The assembly operator then actuates the driver to complete the threadedengagement of all ten of the cap screws 89 at once, until the torquelimit of the individual driver heads is reached at each cap screw 89.

With the ring gear R in place, and all of the cap screws 89 tightened,the entire coupling device 11 is now in the condition shown in FIG. 2.The next step in the assembly process is to place the entire couplingdevice 11 within the axle housing H, one aspect of which is illustratedin the fragmentary view of FIG. 4. What is identified in FIG. 4 as theaxle housing H is in reality the entire axle housing, but minus a cover(not shown herein but put in place at the very end of the assemblyprocess). In the subject embodiment of the present invention, but by wayof example only, the axle housing H defines a pair of surfaces 91 which,relative to FIG. 3, would lie in a vertical plane passing through, or atleast near, the axis of the coupling device. Therefore, when thecoupling device 11 is placed within the differential housing H, the twoanti-rotation tabs 61 each engage an adjacent one of the surfaces 91,thereby preventing any rotation of the coupling device 11 (duringoperation of the vehicle) within the housing H, regardless of directionof rotation of the device.

Referring again primarily to FIG. 4, at the stage of the assemblyprocess represented in FIG. 4, the bearing set 67 is in place about thehub portion 53 (i.e., the condition shown in FIG. 3, as describedpreviously), and as shown in FIG. 4. Typically, but by way of exampleonly, the outer race (not shown herein for simplicity) for the bearingset 67 would already be in place (about the bearing set 67) within thehousing H, and at this stage of the assembly process, a bearing cap (notshown herein) would be bolted into place, by bolts adapted to bethreaded into a pair of internally threaded bores 93. Although not shownherein, it should be understood that the same step of bolting in place abearing cap would be done at the opposite end of the coupling device 11,for the bearing set 67 disposed on the hub portion 65. Once the twobearing caps are bolted in place, the coupling device 11 is basically“installed” within the differential housing H.

The next step in the assembly process is for the assembly operator tomanually seize the tab portion 75 of the oil plug disposed within theport portion 57, and quickly remove both the oil plug 71 in the inletportion 55 as well as the oil plug in the port portion 57. At thispoint, some oil within the coupling device 11 may leak out of the inletportion 55, but at some subsequent step in the assembly process, therequired amount of oil will be introduced into the reservoir within thedifferential housing H. Therefore, as soon as the coupling device 11begins to operate, whatever amount of fluid has leaked out of the devicewill be replaced by fluid being drawn into the device through the inletportion 55.

Once the oil plug is removed from the port portion 57, the next step inthe assembly process is to install the pressure control valve assembly59 (as shown in FIG. 5) by placing the lower, inlet portion 77 into themating opening in the port portion 57, and then manually removing theplastic retainer 83. As may best be seen in FIG. 6, when the retainerportion 85 is no longer holding the radially-extending tabs 81 together,they are permitted to spread, to the position shown in FIG. 6,permitting the expanding clip 79 to open and engage the mating internalgroove within the port portion 57, thus securing the pressure controlvalve assembly 59 in its assembled position.

With the valve assembly 59 in place, a suitable wiring harness (notshown herein) is brought in through a suitable opening in the housing H(not shown herein) and is plugged into the electrical connector 87.Preferably, the wiring harness is disposed to the left (in FIG. 2) ofthe wiring retention tab 66, such that the wiring harness makes contactwith only the stationary plenum member 17, and not with the rotatinghousing (clutch housing 15) of the coupling device 11.

The axle shafts may now be inserted and retained, within and relative tothe side gears 25 and 27, by any of a number of well known axle assemblyand retention methods, which are beyond the scope of the presentinvention. At this point, the process of assembling the coupling device11 within the axle housing assembly H is completed, except for any finalsteps such as attaching the cover mentioned previously over the opening(shown in FIG. 4) of the axle housing H. After the cover is in place,the reservoir would then be filled with fluid, typically through athreaded fitting in the cover. It should be understood by those skilledin the art that many of the recited assembly steps could be performed insome other order beside that set forth herein, except as may bespecifically set forth in the appended claims.

The invention has been described in great detail in the foregoingspecification, and it is believed that various alterations andmodifications of the invention will become apparent to those skilled inthe art from a reading and understanding of the specification. It isintended that all such alterations and modifications are included in theinvention, insofar as they come within the scope of the appended claims.

1. A method of assembly of a coupling device to an input ring gear, foreventual installation within an axle housing, said coupling deviceincluding a housing defining a clutch cavity, a clutch assembly disposedin said clutch cavity, a clutch apply member disposed in a pressurechamber and operable to bias said clutch assembly into torquetransmitting relationship in response to the presence of pressurizedfluid in said pressure chamber; said coupling device including a plenummember operably associated with said housing to define a fluid flow pathproviding fluid communication between a reservoir disposed within saidaxle housing and said pressure chamber, said fluid flow path being influid communication with a source of pressurized fluid; said housingincluding a flange portion defining a plurality of fastener holes andbeing adapted to have said input ring gear attached thereto by means ofa plurality of fasteners; said plenum member comprising a generallyannular plenum portion, and a plurality of required features extendingfrom said plenum portion; said method of assembly comprising the stepsof: (a) configuring said plenum member such that each of said requiredfeatures is disposed circumferentially between an adjacent pair of saidfastener holes; (b) installing said input ring gear about said housingof said coupling device, from an axial end opposite said plenum member,into assembly position adjacent said flange portion; (c) inserting eachof said plurality of said fasteners through one of said fastener holesand into initial threaded engagement with said input ring gear; and (d)driving, by means of a fastener driver, all of said plurality offasteners into full threaded engagement, substantially simultaneously,with said input ring gear.
 2. A method of assembly as claimed in claim1, characterized by one of said required features comprises a fluidinlet portion extending radially toward said reservoir, and furtherincluding an oil plug disposed within said fluid inlet portion, said oilplug further including a tab portion; said method of assembly comprisingthe further step, subsequent to said step (d), of manual removal of saidoil plug, neither said oil plug nor said tab portion blocking access ofsaid fasteners to said fastener holes.
 3. A method of assembly asclaimed in claim 1, characterized by one of said required featurescomprises a valve mounting portion, said coupling device including anelectromagnetic valve member operable to control fluid pressure in saidfluid flow path; said method of assembly comprising the further step,subsequent to said step (d), of operably attaching said valve member tosaid valve mounting portion.
 4. A method of assembly as claimed in claim1, characterized by one of said required features comprises ananti-rotation tab, extending both radially and axially from an endsurface of said plenum member, said axle housing defining a surfacedisposed adjacent said anti-rotation tab, and adapted for engagementtherewith, when said coupling device is installed within said axlehousing.
 5. A method of assembly as claimed in claim 1, characterized byone of said required features comprises a wiring retention tab operableto prevent engagement of a wiring harness with said rotating housing ofsaid coupling device, but to permit engagement of said wiring harnesswith said plenum member.
 6. A coupling device adapted to have attachedthereto an input ring gear, and adapted for eventual installation withinan axle housing, said coupling device including a housing defining aclutch cavity, a clutch assembly disposed in said clutch cavity, aclutch apply member disposed in a pressure chamber and operable to biassaid clutch assembly into torque transmitting relationship in responseto the presence of pressurized fluid in said pressure chamber; saidcoupling device including a plenum member operably associated with saidhousing to define a fluid flow path providing fluid communicationbetween a reservoir disposed within said axle housing and said pressurechamber, said fluid flow path being in fluid communication with a sourceof pressurized fluid; said housing including a flange portion defining aplurality of fastener holes and being adapted to have said input ringgear attached thereto by means of a plurality of fasteners; said plenummember comprising a generally annular plenum portion, and a plurality ofrequired features extending at least partially radially from said plenummember; said coupling device being characterized by: (a) each of saidrequired features is disposed circumferentially between an adjacent pairof said fastener holes, whereby each of said fasteners may be insertedinto its respective fastener opening by moving said fastener along apath substantially parallel to an axis defined by said fastener opening,approaching from the end of said coupling device where said plenummember is disposed.
 7. A coupling device as claimed in claim 6,characterized by one of said required features comprises a fluid inletportion extending radially toward said reservoir, and further includingan oil plug disposed within said fluid inlet portion, said oil plugfurther including a tab portion, neither said oil plug nor said tabportion blocking access of said fasteners to said fastener holes.
 8. Acoupling device as claimed in claim 6, characterized by one of saidrequired features comprises a valve mounting portion, said valvemounting portion defining an opening, and having disposed therein an oilplug including a tab portion to facilitate manual removal of said oilplug, neither said oil plug nor said tab portion blocking access of saidfasteners to said fastener holes.
 9. A coupling device as claimed inclaim 6, characterized by one of said required features comprises ananti-rotation tab, extending both radially and axially from an endsurface of said plenum member, said axle housing defining a surfacedisposed adjacent said anti-rotation tab, and adapted for engagementtherewith, when said coupling device is installed within said axlehousing.
 10. A coupling device as claimed in claim 6, characterized byone of said required features comprises a wiring retention tab operableto prevent engagement of a wiring harness with said rotating housing ofsaid coupling device, but to permit engagement of said wiring harnesswith said plenum member.